Heteranthera limosa (Blue Mud Plantain)
|Also known as:||Ducksalad|
|Family:||Pontederiaceae (Water Hyacinth)|
|Habitat:||part shade, sun; wet; muddy shores, shallow quiet water, vernal pools of rock outcrops|
|Bloom season:||July - August|
|Plant height:||2 to 6 inches|
|Wetland Indicator Status:||GP: OBL MW: OBL NCNE: OBL|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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A single blue-violet to white flower at the tip of a sheathed stalk (spathe). Flowers are up to about 1 inch across, tubular with 6 narrowly elliptic lobes, the upper 3 lobes yellow at the base. Emerging from the tube are a single style and 3 stamens that are glandular hairy along the broad stalk (filament), 1 stamen long and purplish or white, and 2 stamens shorter and yellow. Flowers open just after dawn and wither away by noon.
Leaves and stems:
Leaves are simple and mostly basal, narrowly oblong or narrowly to broadly egg-shaped with a blunt point at the tip, wedge-shaped to rounded to straight across at the base, 3/8 to 2½ inches long, ¼ to 1¼ inches wide. Submersed leaves are mostly stalkless, emersed leaves have sheathed stalks up to 5 inches long and may rise above the water or float on the surface. Stems are creeping and branching from the base, extending to 15 inches, typically submersed in water or buried in mud along the shore, rooting at the nodes and may create dense mats. Flowering stalks are mostly erect.
Fruit is a cylindrical capsule containing oblong, narrowly winged, brown seeds.
In Minnesota, Blue Mud Plantain reaches the northern fringe of its range and is a rare species of ephemeral pools in rock outcrops, located in just a few of our southwest counties. According to the DNR, it was first discovered at Blue Mounds State Park in 1945, then at Pipestone National Monument in 1956, and in Big Stone National Wildlife Refuge during the biological surveys of 2006-2008. The Pipestone population has not been relocated since but it seems to be persisting well at Blue Mounds SP, which is where we encountered it. Due to the rarity of this species in the state, the rarity of its habitat, and risks from grazing and gravel mining, it was listed as a Threatened Species in 1996. Interestingly, it is considered a serious pest plant in the rice fields of California. According to the DNR, the leaves of Minnesota populations tend to be consistently oblong, whereas images and descriptions from other parts of the country show rather broader, egg-shaped leaves. Leaf shape may also vary depending on whether the plant is submersed in water or land-locked in mud. Consequently, it can only be reliably identified when blooming, but that requires adequate moisture for the vernal pools to form so the likelihood of finding it at all varies from year to year.
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Photos courtesy Peter M. Dziuk taken at Blue Mounds State Park, Rock County.
Have you seen this plant in Minnesota, or have any other comments about it?